Project Abstract Cerebrovascular diseases, as one of the leading causes of death and disability in all societies, impose enormous social-economic burden worldwide. Cerebral angiography plays an indispensable role in differential diagnosis, prognosis outlook, therapeutic management, and follow-up after treatment for patients with neurological vasopathology, such as stroke, arterial stenosis, cerebral venous sinus thrombosis , arteriovenous malformation, and aneurysm. Traditionally, catheter-based X-ray angiography has been considered the gold standard for cerebrovascular assessment. Contrast-enhanced (CE) MRA allows large spatial coverage, high spatial resolution, and rapid acquisition. However, arterial visualization are often obscured by venous enhancement. In addition, the safety of Gd based CE MRA has been challenged for the concerns of developing Nephrogenic Systemic Fibrosis (NSF) for patients with impaired kidney function and the reports of Gd deposition in the brain even when no kidney disease is present . Thus non-contrast-enhanced MR angiography (NCE MRA) has rapidly evolved to minimize risk and lower cost. The primary NCE cerebral MRA in clinical practice is the 3D time-of- flight (TOF) method, which is known to have limited angiographic coverage and poor delineation of slow flow. Newly developed arterial spin labeling (ASL) MRA can provide either large spatial coverage or 4D time-resolved MRA with dynamic filling of arteries. The drawback of the ASL methods are the reduced signal efficiency, lengthened scan times due to the required two acquisitions for subtraction of labeled and unlabeled blood signal, and sensitivity to motion-induced misregistration. We recently demonstrated feasibility of a novel velocity- selective (VS) MRA approach for cerebral applications at 3T, which is a non-subtractive technique and allows large coverage and slow-flow depiction. Aiming to incorporate favorable aspects of both TOF and ASL MRA methods, we propose numerous technical advances for VS MRA to render 3D arteriography, venography and 4D time-resolved MRA. The purpose of this study is first to further develop these VS cerebral MRA techniques in flow phantoms and healthy subjects (Aim 1), then to evaluate the 3D VS MR arteriography in patients with carotid or intracranial stenosis (Aim 2) and the 3D VS MR venography in patients with cerebral venous sinus thrombosis (Aim 3), and finally to evaluate the 4D time-resolved VS-MRA in patients with AVM or aneurysm (Aim 4). The proposed NCE VS MRA techniques are expected to show clinical values not only for the brain, but also for the rest of the body, and especially benefit children, pregnant women, and patients with diabetes or impaired kidney function .